Process for production of paper of polyvinyl alcohol synthetic fibers

ABSTRACT

A PROCESS FOR THE PRODUCTION OF PAPER CONSISTING OF A POLYVINYL ALCOHOL FIBER WHICH COMPRISES DISINTEGRATING STABLE FIBERS OF WATER-INSOLUBLE POLYVINYL ALCOHOL AND STAPLE FIBERS OF HOT WATER SOLUBLE POLYVINYL ALCOHOL IN WATER AND THERAFTER MAKING A SLURRY OF SAID FIBERS INTO PAPER, CHARACTERIZED IN THAT PRIOR TO SAID PAPERMAKING STEP, SAID POLYVINYL ALCOHOL FIBERS ARE TREATED WITH A WATER REPELLENT SELECTED FROM THE GROUP CONSISTING OF SILICONE WATER REPELLENTS, COMPLEXES OF HIGHER FATTY ACIDS AND METAL CHLORIDES, ALKYL KETENE DIMERS, METHYLOL AMIDES OF HIGHER FATTY ACIDS AND CATIONIC SURFACE ACTIVE AGENTS.

United States Patent 3,582,462 PROCESS FOR PRODUCTION OF PAPER OF POLYVINYL ALCOHOL SYNTHETIC FIBERS Tadao Ashikaga, Kurashiki, Unpei Maeda, Soji, and Koji Tanaka, Kurashiki, Japan, assignors to Kurashiki Rayon Co., Ltd., Kurashiki, Japan No Drawing. Filed Apr. 15, 1969, Ser. No. 816,413 Claims priority, application Japan, Apr. 19, 1968,

43/216,308 Int. Cl. D21f 11/00; D21h 5/12 US. Cl. 162146 6 Claims ABSTRACT OF THE DISCLOSURE A process for the production of paper consisting of a polyvinyl alcohol fiber which comprises disintegrating staple fibers of water-insoluble polyvinyl alcohol and staple fibers of hot water soluble polyvinyl alcohol in water and thereafter making a slurry of said fibers into paper, characterized in that prior to said papermaking step, said polyvinyl alcohol fibers are treated with a water repellent selected from the group consisting of silicone water repellents, complexes of higher fatty acids and metal chlorides, alkyl ketene dimers, methylol amides of higher fatty acids and cationic surface active agents.

This invention concerns a process for the production of paper of polyvinyl alcohol synthetic fibers. More particularly, it relates to a process for the production of paper of polyvinyl alcohol synthetic fibers having good formation and excellent strength which comprises treating polyvinyl alcohol synthetic fibers with a water repellent before making an aqueous slurry of said fibers into paper to impart an enhanced papermaking ability to said fibers.

It has generally been known to produce paper from a polyvinyl alcohol fiber by disintegration in water of staple fibers of water-insoluble polyvinyl alcohol and staple fibers of hot water soluble polyvinyl alcohol, and making a slurry of these fibers into paper. Generally, polyvinyl alcohol synthetic fibers are most hydrophilic of all synthetic fibers, and can be made into paper by a customarily used paper machine. But their papermaking ability would not be better than those of bast fibers such as wood pulp, Manila hemp and Mitsumata (Edgeworthia papyrifera). Furthermore, comparison of the polyvinyl alcohol synthetic fibers with one another will reveal that those having a higher degree of molecular orientation and higher degree of crystallinity have a lower degree of papermaking ability.

We have unexpectedly found that when a polyvinyl alcohol synthetic fiber is treated with a specific water repellent, such as silicone water repellents, complexes of higher fatty acids and metal chlorides, metal soap, alkyl ketene dimers, methylol amides of higher fatty acids and cationic surface active agents, prior to making an aqueous slurry of said fiber into paper, the papermaking ability of said polyvinyl alcohol fiber is remarkably enhanced, and the formation and strength of the obtained paper are also markedly improved.

Accordingly, the invention provides a process for the production of paper consisting of a polyvinyl alcohol fiber which comprises disintegrating staple fibers of Water-insoluble polyvinyl alcohol and staple fibers of hot water soluble polyvinyl alcohol in water and thereafter making a slurry of said fibers into paper, characterized in that prior to said papermaking step, said polyvinyl alcohol fibers are treated with a water repellent selected from the group consisting of silicone water repellents, complexes of higher fatty acids and metal chlorides, alkyl ketene "ice dimers, methylol amides of higher fatty acids and cationic surface active agents.

The water-insoluble polyvinyl alcohol fibers used in the invention are those obtained by wetor dry-spinning polyvinyl alcohol having a degree of polymerization of 1500 to 2500 using a method known per se, stretching and orienting the obtained fibers, and thereafter heat-treating the oriented fibers, or those obtained by further formalizing the heat-treated fibers. It is desirable that the starting polyvinyl alcohol should be one resulting from complete saponification of polyvinyl acetate. For rendering polyvinyl alcohol fibers water-insoluble, it will be sufficient to heat-treat them, for instance, at a temperature of 220- 240 C. for a period of time on the order of several seconds to several minutes. The formalization of the polyvinyl alcohol fibers may be carried out under conditions known per se, but to achieve the objects of the present invention, it is preferable to formalize 30-40 mole percent of the hydroxyl groups in the polyvinyl alcohol fibers. The formalization can be effected in an aqueous solution containing formaldehyde, mineral acids, for' instance, sulfuric acid, and such a neutral salt as Glaubers salt at a temperature of 50 to C. The size and length of the water-insoluble polyvinyl alcohol fiber are preferably 0.7 to 6 denier, and especially about one denier, and 3-7 mm., respectively, although varying depending upon the kind of paper obtained as a final product.

In the present invention, polyvinyl alcohol fibers soluble in hot water are used as binder together with said water-insoluble polyvinyl alcohol fibers. Preferable as such binder fibers are those having a water solubilizing temperature of 50 to C. By the term water solubilizing temperature, used herein, is meant a temperature of water at which the polyvinyl alcohol fibers are substantially dissolved in the water. The hot water soluble polyvinyl alcohol fibers can be obtained by wetor dry-spinning a partially saponified or completely saponified polyvinyl alcohol having a degree of saponification of 98-100 mole percent and a degree of polymerization of 500 to 2000 in a. customary manner, drawing and orienting the obtained fibers, and if necessary, drying the as-spun fibers. It is preferable that generally the size of the hot water soluble polyvinyl alcohol fiber should be 1 to 2 denier, especially about one denier, and its length, 2 to 4 mm., especially about 3 mm.

It is preferred that the water-insoluble polyvinyl alcohol fibers (A) and the hot water soluble polyvinyl alcohol fibers (B) should be used in the following proportions, namely,

A: 70-95% by weight, particularly 75-85% by weight,

B: 305% by weight, particularly 25-15% by weight. Proportions outside the above specified ranges will lead to deterioration of the mechanical properties and formation of the resulting paper.

According to the process of the present invention, the water-insoluble polyvinyl alcohol fibers and the hot water soluble polyvinyl alcohol fibers are disintegrated in water at a paper stock concentration of about 2% by a procedure known per se. The disintegration may be conducted by using a known apparatus such as a disintegrator, pulper, beater and refiner. The obtained aqueous slurry of the fibers is diluted with Water to provide a paper stock concentration of 0.1 to 0.2% at the time of papermaking.

The important feature of the present invention lies in the treating of polyvinyl alcohol fibers, prior to making an aqueous slurry of said fibers into paper, with a specific water repellent selected from the group consisting of silicone Water repellents, complexes of higher fatty acids and metal chlorides, metal soap, alkyl ketene dimers, methylol amides of higher fatty acids and cationic surface active agents. Polyvinyl alcohol fibers are most hydrophilic among synthetic fibers. It has however, been found that when the polyvinyl alcohol fibers are distintegrated in water, a satisfactory dispersion can be obtained, but when the obtained fiber slurry is made into paper, the fibers tend to be reflocculated. However, if the polyvinyl alcohol fibers are treated with the above-mentioned specific water repellent prior to the paper-making step, flocculation of the poly-vinyl alcohol fibers is unexpectedly prevented, and their dispersibility is markedly improved. The paper of polyvinyl alcohol fibers produced according to the process of the invention therefore has a better formation and more excellent properties such as tensile strength, tearing strength, bursting strength and folding resistance than the conventional polyvinyl alcohol fiber papers. Such advantages of the present invention cannot at all be anticipated from a mere idea of treatment with a water repellent.

Any silicone water repellent conventionally used in water repelling treatment of fibers may be used in the present invention. Such silicone water repellents include organopolysiloxane oil and a liquid of a siloxane/oxyalkylene block copolymer wherein the siloxane block is connected to the oxyalkylene block via an oxygen atom or a carbon atom. The organopolysiloxane has the recurring units expressed by the general formula RI s i-o wherein R is a monovalent hydrocarbon group, and R is a hydrogen atom or monovalent hydrocarbon group.

In addition to organopolysiloxanes having the abovementioned recurring units, such as dimethyl polysiloxane and methyl hydrogen polysiloxane, it is also possible to use organopolysiloxanes having the siloxane units with such functional groups as an aminoalkyl group and epoxy group as the organo group. The siloxane/oxyalkylene block copolymer usable in the present invention is one described, for instance, in US. patent application Nos. 2,846,458, 2,965,515 and 2,917,480.

These silicone water repellents are used in the form of an emulsion, varnish or a solution in an organic solvent for the treatment of polyvinyl alcohol fibers.

As the complexes of higher fatty acids and metal chlorides used in the present invention, we may cite complexes of saturated or unsaturated higher fatty acids having 12 to 24 carbon atoms, such as palmitic acid, stearic acid and oleic acid, and chlorides of aluminium or chromium. These complexes may be Werner coordinate compounds, such as one expressed by the formula wherein the arrows show coordination, and R is an aliphatic hydrocarbon group having 11 to 23 carbon atoms. As the complex salt of chromium chloride assumes a green color, it is especially advantageous to use a complex salt of aluminium chloride which is colorless. These complexes are dissolved in a water-miscible organic solvent such as isopropyl alcohol, and the resulting solutions are dispersed into water to form emulsions with which polyvinyl alcohol can be treated. As the metal soap which can be conveniently used, we can mention those consisting of saturated or unsaturated higher fatty acids having 12 to 24 carbon atoms, such as palmitic acid, stearic acid and oleic acid and divalent or trivalent metals, such as calcium, magnesium, lead manganese and aluminium.

The alkyl ketene dimers conveniently usable in the present invention is expressed by the following general formula RCH=C-OHR 'wherein R is a saturated or unsaturated alkyl group having 12-24 carbon atoms.

Such alkyl ketene dimers can be produced by reacting corresponding fatty acid chlorides in the presence of an acid binder. It is known that these alkyl ketene dimers react with polyvinyl alcohol fibers in accordance with the following formula, for instance,

The methylolamides of higher fatty acids usable conveniently in the present invention are expressed by the following general formula wherein R is a saturated or unsaturated alkyl group having 11 to 23 carbon atoms.

As the cationic surface active agent, we can use such cationic surface active agents as long-chain alkyl pyridinium halide, long-chain alkoxy methyl-pyridinium chloride, alkyl trimethyl-ammonium chloride, and long-chain alkyl dimethylbenzyl ammonium chloride. But particularly preferred is a long-chain alkyl amide methyl pyridinium chloride expressed by the formula nooNHoH2N+or wherein R is a saturated or unsaturated alkyl group having 11 to 23 carbon atoms.

The surface treatment of polyvinyl alcohol fibers with such Water repellents may be effected at any stage prior to the papermaking step. For example, the water repellent is applied to polyvinyl alcohol fibers in the form of an emulsion or solution to thereby coat the water repellent onto the surface of the fibers. The application of the water repellent can be effected in a manner known per se, such as by spraying and dipping. It is possible in the present invention to cause the water repellent to adhere only to the Water-insoluble polyvinyl alcohol fibers. Alternatively, the water repellent, its solution or its emulsion may be added to an aqueous slurry of polyvinyl alcohol fibers to effect the water repelling treatment. The time of addition of the water repellent is not particularly restricted, and may be, for instance, before, during (for instance, at the stages of beater and poacher) and after (at the stages of head-box and bat) disintegration.

The amount of the water repellent to be adhered or added to polyvinyl alcohol fiber may be in the range of 0.1 to 3% by weight based on the fibers, and an optimum amount for each water repellent can be determined by a simple experiment. The water repellents specified in the present invention have remarkable functions of facilitat ing the dispersion of polyvinyl alcohol fibers and prevent reflocculation of the fibers occurring during the papermaking process. Polyvinyl alcohol fibers are hydrophilic, and it is expected that water repelling treatment of these fibers will result in the deterioration of their dispersibility in water. Contrary to such expectation, however, the abovementioned water repellents enhance the dispersibility of polyvinyl alcohol fibers in water.

It has been known to use rosin and rosin derivatives such as maleic rosin as a sizing agent in the manufacture of paper from cellulosic fibers for the purpose of imparting water proofness and graphic properties to such paper. It is true that these sizing agents are water-repellent in nature, but addition of rosin, for instance, to an aqueous slurry of polyvinyl alcohol fibers, as will be mentioned in the Comparative Example appearing later in the pages, cannot lead to the prevention of flocculation of the fibers and the improvement of formation of the resulting paper.

In the process of the present invention, ordinary papermaking conditions used in making paper from polyvinyl alcohol fibers may be employed. The concentration of an aqueous slurry of the fibers used in the papermaking may be from 0.1 to 0.2%. It is also possible to use hibiscus tackifier or a chemical tackifier such as polyethylene oxide, potassium metaphosphate and poly(sodium acrylate) generally employed in papermaking. Such tackifier can be used in an concentration customarily used, such as 0.0001 to 0.00003% by weight. The papermaking can be carried out by any apparatus which is capable of separating fibers from their aqueous slurry on a Water-filtering net and forming a thin layer of intertwined fibers, such as Fourdrinier paper machine, cylinder paper machine and short net type paper machine. Paper of polyvinyl alcohol fibers from a drying drum of a paper machine is passed through a calender as required, and cut to make a final paper product.

The invention will now be described with reference to the following non-limitative examples.

EXAMPLE 1 Eighty parts of polyvinyl alcohol fibers (1 denier, cut to a length of mm.) having a degree of formalization of 30% and having adhered thereto 0.5 calculated as silicone, of a silicone water repellent (varnish dimethyl siloxane, Polone A, product of Shinetsu Chemical Industries, Co., Ltd., Japan), and parts of polyvinyl alcohol fibers having a water solubilizing temperature of 60 C. and cut to a length of 3 mm. were made into paper by a wet method. As a control, a paper stock consisting of the same polyvinyl alcohols but not containing a water repellent was also made into paper in the same manner. It was found that paper from the water repellent treated stock has a more uniform and better formation than paper from the non-treated stock.

EXAMPLE 2 A paper stock consisting of 85 parts of polyvinyl alcohol synthetic fibers (1 denier, 5 mm.) which had been hot drawn and hot shrunken and 15 parts of polyvinyl alcohol fibers (l denier, 3 mm.) having a water solubilizing temperature of 70 C. was prepared. To the resulting paper stock was added an alkyl ketene dimer of the formula Cl6H33CH=(|:OH-C1H33 O-C=O in an amount of 0.5 and 1%, respectively. The mixture was made into paper having a weight of 63 g./m. A stock of the same composition but without the water repellent was also made into paper in the same manner. The tensile strength and tearing strength of each paper were measured, and the results are shown in Table 1.

It is seen from the results that paper from the nontreated paper stock has a tensile strength in the machine direction of 12.2 kg./ 15 mm., but the paper of the invention from the 1% water repellent treated stock is excellent in formation has a tensile strength of 13.8 kg/ 15 mm.

6 EXAMPLE 3 Polyvinyl alcohol was spun by using sodium hydroxide as a coagulating bath, and the spun filament was hot drawn and hot shrunken. To 90 parts of the so prepared polyvinyl alcohol fibers (1 denier, cut to a length of 3 mm.) were added 0.5% or 1%, based on the fibers, of stearic acid aluminium chloride (a complex of stearic acid and AlCl at a ratio of 1:2), and 10 parts of polyvinyl alcohol fibers (l denier, cut to a length of 3 mm.) having a water solubilizing temperature of C. The time required for 0. 02% suspensions to disperse uniformly and their paper-making ability were measured. The results are given in Table 2.

formation good. 36 Much flocculation of fibers; formation bad.

Control (non-treated fibers) It is seen from the foregoing that the non-treated fibers took 36 seconds to disperse uniformly and underwent flocculation in the paper-making process, whereas the fibers treated by the process of the invention dispersed completely in 11 to 18 seconds and it was possible to make paper having a uniform formation without undergoing flocculation.

COMPARATIVE EXAMPLE Polyvinyl alcohol -was spun by using sodium hydroxide as a coagulating bath, and the spun fibers were hot drawn and hot shrunken. To parts of the so prepared fibers having excellent transparency and resistance to hot water (1 denier, cut to a length of 3 mm.) were added 0.5% or 1%, based on the fibers, of rosin and 10 parts of polyvinyl alcohol binder fibers (1 denier, cut to a length of 3 mm.) having a water solubilizing temperature of 80 C. The time required for 0.02% suspensions to disperse uniformly and their papermaking ability were measured.

The results are shown in Table 3.

polyvinyl alcohol fibers (1 denier, 5 mm.) treated with 1% of stearic acid aluminium as a water repellent and 20 parts of polyvinyl alcohol binder fibers (l denier, 3 mm.) having a water-solubilizing temperature of 70 C. and a paper stock of the same composition but not containing the water repellent were each made into paper by a wet method. It was found that the water repellent treated stock was good in papermaking ability and gave paper of a uniform formation as compared with the nontreated paper stock.

EXAMPLE 5 A paper stock consisting of 90 parts of polyvinyl alcohol fibers (1 denier, 5 mm.) having a degree of formalization of 32% and having adhered thereto 1.0%, based on the fibers, of methylol palmilamide and 10 parts of polyvinyl alcohol fibers (3 mm.) having a water solubilizing temperature of 60 C., and a paper stock of the same composition but not containing the water repellent were each made into paper, and they were compared with each other in respect of papermaking ability. It was found that paper from the non-treated stock was not uniform in formation, whereas paper from the water repellent treated stock has a good formation.

EXAMPLE 6 Eighty parts of polyvinyl alcohol fibers (1 denier, mm.) which had been heat-treated and 20 parts of polyvinyl alcohol binder fibers (1 denier, 3 mm.) having a water solubilizing temperature of 70 C. were disintegrated at a concentration of 2% then, 1%, based on the fibers, of stearamide methyl pyridinium chloride was added. The so treated paper stock was diluted to a stock concentration of 0.13% after treating in a beater, and made into paper having a weight of 25 g./m. It was very easy to make-up the formation of paper from this paper stock.

On the other hand, it was found that a paper stock of the same composition but containing no water repellent did not give a good formation.

We claim:

1. A process for the production of paper consisting of a polyvinyl alcohol fiber which comprises disintegrating staple fibers of Water-insoluble polyvinyl alcohol and staple fibers of hot water soluble polyvinyl alcohol in water and thereafter making a slurry of said fibers into paper, characterized in that prior to said papermaking step, said polyvinyl alcohol fibers are treated with a water repellent selected from the group consisting of silicone water repellents, complexes of higher fatty acids and metal chlorides, alkyl ketene dimers, methylol amides of higher fatty acids and cationic surface active agents.

2. The process according to claim 1 wherein the hot water soluble polyvinyl alcohol staple fibers have a water solubilizing temperature of to'90 C.

3. The process according to claim 1 wherein the ratio of the water-insoluble polyvinyl alcohol staple fibers to the hot water soluble polyvinyl alcohol staple fibers is in the range of -95% by weight: 30-5 by Weight.

4. The process according to claim 1 wherein said water repellent is applied in an amount of 0.1 to 3% by weight based on the fibers.

5. The process according to claim 1 wherein the water repellent is organopolysiloxane oil.

6. The process according to claim 1 wherein the water repellent is a complex of a higher fatty acid having 12 to 24 carbon atoms and aluminium chloride.

References Cited UNITED STATES PATENTS 2,810,645 10/1957 Houghton 162157C 3,114,670 12/1963 Iwasaki 162-146 3,354,032 11/1967 Sommer et al 162146 3,401,078 9/1968 Grossteinbeck et al. 162-146 HOWARD R. CAINE, Primary Examiner US. Cl. X.R. 

